While in Budapest we had several dinners with my sister, her husband and their two kids - and they are all vegetarians. After eating at several Hungarian restaurants we realized their options were very limited and that perhaps they wanted to eat something besides fried cheese and fried mushrooms.
We asked a vegetarian we knew and he said the options are Indian or Italian and so we chose Indian and ended up at Salaam Bombay h-1051 budapest merleg utca 6 tel 411 1252
I did not have high hopes - we lived in India for a year and most Indian restaurants we try are unsatisfying, but we were very encouraged to find out the chefs were from Kolkutta and Delhi - and in fact the food was really good. We walked in with no bookings, eight people and they seated us and were very friendly and helpful and it was such a joy to have a variety of vegetarian food.
Not what I would normally choose, but for vegetarian food in Budapest it would be my number one suggestion.